But the screens should look different, right? That's the point of building separate iOS vs. Android versions is to make each version "native" to its platform. The feature-set should be the same, but the interfaces can diverge.

I think the whole native thing is more for better performance, debugging ease and dependency reduction rather than seeking variation in UIs.

It is both. You want the application to look correct on the platform the user is on, i.e. Liquid Glass on iOS and Material on Android.